Many anaIytical methods have been used to identify the chemical composition of archaeological artefacts [1-4]. Museum CIRTA of the town of Constantine has a collection of more than 35000 coins and statuettes going back to Numide, Roman, Republican, Vandal and Byzantine times and is struck in the name of the cities, of the kingdoms and the empires. Surface analysis of these coins gives informations about the chemical composition and leads to recommendations for restoration and presevation. This work is a contribution of microchemical surface study of three coins with the effigy of the Numide King Massinissa (between 3rd and 2nd century before Jesus Christ). Scanning electron microscopy coupled with energy dispersive spectrometry (SEM + EDS) and energy dispersive fluorescence spectrometry (XRF) were used. The bulk of three coins is massif homogeneous metallic. Two coins are manufactured with lead (99.896% and 61.56%) and were probably conserved differently. The third one is from copper (92.28%). The optic microscopy (OMP) and SEM pictures of coins show heterogeneous surface with typical lead alteration products white patina of plumbonacrite, cerussite and hydrocerussite and red patina of cupric oxide on the cupric artefact. MS25 P09 Effects of Er 3+ and Yb 3+ doping on phase transitions of LiNH 4 SO 4 .

The crystalline network that characterizes the family of ferroic materials of the kind of ALiSO4 (A=Na, NH4, K) has a great flexibility, which facilitates the existence of phase transitions and non-linear properties. However, lately, the research has been basically directed to the ionic conductivity these networks present. The work we present here is a part of a research line on the effects of rare earths in non-linear matrixes due to their great technological interest. The study of the structural properties due to the doping of LiNaSO4 with Yb +3 and Er +3 were performed by Palmero et al. (J. Luminic. 128, 2008). The doped compounds showed no important structural differences in relation to the pure ones. Apart from that and for the first time, they observed second harmonic generation (SHG) in all cases. In what refers to LiNH4 SO4, Gonzalez-Silgo et al. (2008. In Press), found two new alpha phase polimorph isotypes of the Li(NH4)1-2X YbXSO4 doped compound, which present SHG. In this work, the Lithium-Potassium sulphate has been analysed using the same procedures and experimental techniques as in previous cases (RX, TG-DTA, DSC and SHG). The structural differences observed in the compounds doped with Yb +3 and Er +3 show some rotation with respect to the pure one. The data obtained from the three sulphates allow us to present a comparative study on the Yb +3 and Er +3 doping effect in relation to their non-linear optical properties in the context of the structure and the temperature behavior. The results are quantitatively discussed in two different ways: using the Bond-Valence Sum (BVS) model and the Abraham-Kurt-Jamienson criterion, which are compared with the model presented by Xue and Zhangs (Phys. B 262, 1999) for non-linear compounds.